On the impact of mobility on the channel estimation in WiMax OFDMA-uplink

The demand for wireless broadband access systems supporting mobility of the individual users has dramatically increased in recent years. To this end, we analyze the impact of user-mobility in the uplink of an OFDMA system on the performance of pilot-aided channel estimation. We analyze the mean square error (MSE) performance of two pilot-aided channel estimation schemes, the simple Gauss-Markov estimator and the optimal LMMSE estimator. We derive closed-form expressions for the MSE taking into account the impact of intercarrier-interference and time-variations of the channel. Different pilot allocation strategies are analyzed and their performances are compared. Finally, the results are illustrated by numerical simulations based on the WiMax 802.16e specifications.